Usability

„Usability: the extent to which a product can be used by specified users to achieve specified goals with effectiveness, efficiency and satisfaction in a specified context of use.“

A definition by Joseph Dumas and Janice Redish:

„Usability means that the people who use the product can do so quickly and easily to accomplish their own tasks. This definition rests on four points:
1. Usability means focusing on users.
2. People use products to be productive.
3. Users are busy people trying to accomplish tasks.
4. Users decide when a product is easy to use.“

A definition by Jakob Nielsen:

„Usability is the measure of the quality of the user experience when interacting with something  whether a web site,
a traditional software application, or any other device the user can operate in some way or another.“

In the context of the World Wide Web Usability means according to Benjamin Keevil:

„how easy it is to find, understand and use the information displayed on a Web site“.

In the context of Web Sites Usability means according to Jared Spool et al.:

„Whatever the goal, information is a central theme. For intranets (internal web sites), information is the theme  no one surfs the online employee policy manual just for kicks.
Because of this, we focused our study on how successful sites are at providing people with information so they can make decisions. The more a site helps people find the
information they are looking for, the more usable it is.

Sienot, M. (1997): Pretesting Web Sites. A Comparison Between The Plus-Minus Method And The Thinking-Aloud Method For The World Wide Web. In: Journal of Business and Technical Communication, 11 (4), 469-482.